Rostock V2 Thermistor Negative Tempuratures

[ShaneTBaker]

I just completed the assembly of my new HE280, but on first boot the thermistor is reading -50, then def. I checked all connections, resistance across thermistor, checked for shorts and tried the troubleshooting on the thread link below for someone with the same issue.

http://forum.seemecnc.com/viewtopic.php?t=4576

To sum up that thread, I chacnged from T0 to T1 port on the rambo and adjusted the firmware to allow that change. Same error, so I think I can eliminate that my issue is the board. I am not getting the same results, so I am not sure what to try.

[geneb]

If you're not using the 1.6.1 version of the Arduino IDE, try that. Also, make sure the thermistor wires at the RAMBo and at the hot-end end of the wiring harness are correct.

Does the bed thermistor read room temp (in C)? If so, try connecting the hot end thermistor to the heated bed thermistor port on the rambo - if the negative value follows, you most certainly have either a wiring problem or a bad thermistor.

g.

[ShaneTBaker]

So I have the updated arduino, the wiring is correct but I did make an improvement. My tempurature is now reading and tracking tempurature changes. However, the room temp is reading ~10.0C whereas its about 25C in my room

[Xenocrates]

Thermistors are not linear devices. They are also imperfect. The ones used in 3D printing are chosen for stable high temperature performance and to be sensitive and usable at the temperatures required. Room temperature sensing is therefor only approximate. You might have a cold solder joint increasing the effective resistance, and thus lowering the measured temperature. That's easy enough to check with a multimeter. Just check the resistance at the terminals and each joint along the path. It may simply be a thermistor off the nominal value enough at that temperature. If it's correct at the operating temperature (Use a thermocouple to check this, or a thermometer), then don't worry much. Otherwise, replace the thermistor/wiring.

[rootboy]

Did you disconnect it from your Rambo board and measure the resistance? You need to do this from the top end so that you measure the resistance of the wires as well as the thermistor itself (in case they have broken, which they will do eventually).

[geneb]

They only break under stress. If they're properly installed, they're never under stress so won't break.

g.

[rootboy]

Or when those stupid pins that hold the Effector Platform to the Delta Arms work their way out (yet again) and the platform drops down and smacks your print and knocks it off of the heated bed, that will do it too. It didn't break the thermistor itself, but pulled apart the tiny wire going to it.

But anyone in automation who works around robots knows that the cables will wear out. Most places schedule their replacement on a yearly basis. The same thing applies to fixtures that to open and close. Bottom line is that if you have a cable that bends, sooner or later the wires will break.

[geneb]

Sounds to me like a) you're using the really old u-joint arms and b) you don't have the retaining clip installed on the pin properly.

Upgrade to the ball-joint arms & injection molded carriages (if you've got the old melamine ones) It's like getting a whole new printer for around $80.

I've never once in five years seen an instance of wire failure due to fatigue, nor have I ever heard of it happening - at least with stranded wire. The bending stress on the wiring harness simply isn't enough to induce a fatigue failure within the lifetime of the printer (and likely the printer user).

Can it happen? Sure, anything can happen. It's just not likely to happen.

g.

[rootboy]

Well, I'm using what came with the kit, and the clips are in the way that they are supposed to be. I've got kapton tape holding the pins in for the time being, which looks ugly, but it is doing fine. I've got all of the parts for converting it to carbon fiber rods, so I'll probably work on that next week.

Broken wires are one of the constants in the automation industry. At the last place that I worked, the ASRS crane, a Fanuc M-10iA robot, a brake pad depth gauge, the clamping fixture sensors for holding down the spacer blocks on the headliner while the hot-melt glue sets, and a hot-melt glue applicator all had their cables break in a three month period. Obviously they are not big on doing their PMs. With the Fanuc and ASRS cables costing about $3000 - $5000 each, I can sort of see their point...

You also see it happening with the wires that go from the frame of your car to the door, as well as the sensor wires to anti-lock brakes. The symptoms are intermittent faults while the wheels are turned a certain way at first, with the problem getting worse as time goes on. Or, in the case of the door, your window and locks stop working. The failure point can be hard to detect until you pull on the suspect wire. It will stretch and then break the insulation at the point when the wire is broken.

You can buy cable that is designed for 10's of millions of cycles. Olflex is one brand that I have used. Along with the number of strands (the more the merrier), the insulation and even what's between the insulation and the wire (often paper to reduce friction) makes a big difference. TQ Wire sells a 16 gauge wire with 665 strands for slot cars.

[geneb]

If the clips are installed properly, there's no way those pins can move. Could you post a pic of the clip installation?

tnx!

g.

[rootboy]

Here's a shot from the bottom up. I really don't want to take the Tape off for a better shot since it's working fine as is.

The clips snap in around the rod, so I can't see any other way they would go in...

For some reason it didn't load the picture. Let's try it again...

[geneb]

It looks like they're installed ok - but it's really hard to tell.

If they're sliding out of the u-joints, there may be some galling going on with the metal u-joint. I would /highly/ recommend you upgrade to the ball & socket arms and the injection molded carriages. It will greatly improve the performance of the machine over the original metal u-joint design.

g.

[rootboy]

Thanks! But since I've already have the parts for the carbon rod upgrade, I'll try that first.

But it really is doing fine as is.

[geneb]

If the arms are as tight as the ball & socket ones, your definition of "fine" is going to be altered...greatly.

g.

[rootboy]

I'm looking forward to it!

Most of the slop that it still has seems to be in the cheapskates. I just tightened them up and it seems to have helped. I'm going to do a 100mm calibration block to see how close I can get.

The last time it was 99.8 along one end, and 98.4 along the other.

[rootboy]

First off, apologies to the OP. Did you get your hotend working?

I'm a bit closer, about 1 mm difference between the two ends. About a 1/2 mm improvement.